Method of treating liquid distillates.



UTED STATES PATENT FIE.

FREDERICK W. SPERB, JR., F OAKMONT, PENNSYLVANIA, ASSIGNOR TO H. KOPPEBS COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF MAINE.

METHOD OF TREATING LIQUID DISTILLATES.

No Drawing.

To all whom it may concern:

Be it known that I, FREDERICK W. Srnnn, Jr., a citizen of the United States, residing at Oakmont, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in the Methods of Treating Liquid Distillates, of which the following is a full, clear, and exact description.

My invention relates to the treatment of distillates from a liquid mixture, particularly the treatment of the distlllates of light oil, obtained from coal tar, gas, etc, though it may be applied to other mixed distillates.

Light oil in the sense here used, is 011 containing benzol, toluol, light naphtha, etc.

Ileretofore in treating light oils the usual practice has been to first distil ofif crude benzol to a temperature of approximately 100 C., then the crude toluol fraction was distilled off to approximately a temperature of 120 C., and finally the crude solvent naphtha fraction was distilled off to approximately a temperature of 160 0., or higher if desired. Each of these crude fractions has then been separately washed to purify them, the treatment usually lncluding the steps of treating with concentrated sulfuric acid, then washing with water, then treating with caustic soda solution, again washing with water and finally redistilling.

In this usual method, considerable difhculty is experienced in purifying the distil-' lates which are of a higher boiling point than toluol, principally on account of the amount of emulsification which occurs and the large quantities of sticky residue re maining in the still after th1s redistillation of the washed high boiling point distillates. These high boiling point distillates from light oils contain relat1vely larger quantities of the impurities forming the sticky residue, than do the lower boiling point distillates such as benzol and toluol.

I have found that I can overcome the diiiiculty in treating such distillates producing sticky residues by my inventlonand Wlll. now describe it as applied to treating light oil, for example, that which 1s recovered from coal gas by the so called scrubbing process.

I first distil the light 011 to a temperature of approximately 120 C. so as to obtain a Specification of Letters Patent.

mixture of crude benzol and crude toluol in one fraction. Thereafter, I raise the temperature and distil off the higher boiling point materials in one or more fractions, including the crude solvent naphtha fraction.

I then wash the mixed crude benzol and toluol fractions with concentrated sulfuric acid until sufiiciently pure, treatment with water and caustic soda solution being unnec: essary at this stage. In determining whether the material is suificiently pure, the operator may, for example, proceed as follows: First wash the mixed crude benzol and toluol fraction by agitating with successive smaller quantities of concentrated sulfuric acid, the first quantity being used being equivalent to 1.5 per cent. of the light oil; then follow with a quantity of sulfuric acid equivalent to about 1 per cent. of the light oil,then take a small sample of the light oil, shake it with water in a separatory funnel, draw 03 the water, shake the'sample with a small amount of caustic soda solution, draw this off, and then shake with water and draw this off. Then distil the sample at a temperature of about 115 degrees (3., put part of the distillate in a small bottle, add about twice its volume of concentrated sulfuric acid, shake for a few minutes, and then allow the mixture to stand.

The purity of the distillate is indicated by the color of the material in the bottle. The usual specifications prescribe that the acid layer shall be only slightly cooled, and that the oil layer shall be water white. If the operator finds by this test that the treatment of the mixed fraction with sulfuric acid is sufficient, he proceeds with the treatment with water and caustic soda solution, etc. If, however, the test shows that the product would not be sufficiently pure, the test samples showing a deep yellow or reddish color on shaking the sulfuric acid, the treatment of the main quantity of the mixed fraction is continued by adding another one per cent. of sulfuric acid and agitating. He

then takes another sample, makes another test, and so on, until the washed distillate is sufficiently pure.' I then add to the washed fractions a desirable proportion of any one or more of the higher boiling point fractions. I then treat the mixture with concentrated sulfuric acid until the desired degree of purity is obtained, after which I Patented Nov. 313, 1917. Application filed November 26, 1915. Serial No. 63,694.

continue the washing in the usual manner, preferably with water, followed by caustic soda solution and finally water.

I thus obtain a mixture of comparatively pure lower boiling point distillates and higher boiling point distillates. I then redistil this mixture with an efficient distillation apparatus and separate the pure benzol, toluol and higher boiling point-fractions successively in the usual manner.

In practice, I have found it desirable to add the higher boiling point distillates to the partly washed lower boiling point distillates in approximately the original proportion which they bear in the light oil. If, however, the higher boiling point distillates contain excessive amounts of impurities, I may mix a smaller proportion with the partly washed lower boiling point distillate. The mixture may then be treated with sulfuric acid, a further proportion of higher boiling point distillate added followed by further treatment with sulfuric acid and so on until all of the higher boiling point distillates have been used up. This treatment may be followed by washing with water and caustic soda solution and redistillation as above described.

I may, in some cases, redistil the crude higher boiling point fractions above toluol before combining with the partly washed lower boiling point fraction.

'1 will now describe a specific example of carrying out my process:

Taking a typical light oil from coke oven gas, I distil a thousand gallons of such light oil and obtain 750 gallons of fraction A distilling under 120 0.; 190 gallons of fraction B distilling between -l20' C. and 200 (1.; and 60 gallons of residue. The residue is discarded.

I put the 750 gallons of fraction A in a lead lined agitating vessel and agitate it with l% of its volume of concentrated sulfuric acid, preferably in three successive portions or additions. After agitation with each portion of acid, the mixture is allowed to settle and a heavy acid sludge is drawn off from the bottom of the vessel.

After these operations I make the laboratory test above described. Usually at this stage the test will show a satisfactory resalt, but if it does not, I again agitate the fraction A with an additional 1% of its volume of concentrated sulfuric acid, draw off the sludge and repeat the test, continuing this method of treatment with successive agitations of acid until the test gives a satisfactory result.

I then add to the fraction A thus treated the entire 190 gallons of fraction B and agitate the mixture with 2% of its volume of concentrated sulfuric acid. After allowing it to settle and drawing off the sludge from the bottom, I test the mixture as before I then redistil this purified mixture and i obtain pure benzol, toluol, xylol, and solvent naphtha at a single operation in about the following proportions:

580 gallons of pure benzol, 130 gallons of pure toluol, gallons of pure xylol, 70 gallons of solvent naphtha.

I also obtain about 20 gallons of .residue which is discarded, and about 120 gallons of intermediate fractions.

If the usual old type method had been followed and the 190 gallons of fraction B treated separately, much trouble would have been found with emulsification in the agitating vessel and with the formation of a heavy sticky residue in the subsequent process of distillation. These difficulties are overcome by my process.

The advantages of my invention result from the mixing of the crude higher boiling point fraction or fractions with partly washed lower boiling point fraction or fractions and the consequent dilution of any impurities present. The impurities of the higher boiling point fractions are, in my process, diluted by mixing with the already partly purified lower boiling point fractions, this simplifying and making easier the complete purification. This method reduces or removes the difficulties heretofore present in purifying the higher boiling point fraction or fractions above toluol, since the sticky residue is done away with or reduced.

Such residue in my process is less in proportion than in the former process and is, moreover, in a fluid, oily condition relatively easy to handle.

The difficulty resulting from emulsification in the former treatment of these higher point distillations is also. removed. The labor and expense of separately purifying the higher boiling point fractions above toluol is saved, as their purifying is combined with the purifying of the lower fraction. I also find that there is a considerable increase in the yield of some of the higher boiling point fractions above toluol. such as solvent naphtha.

My invention may be used to advantage in treating other volatile liquid mixtures containing impurities capable of being removed, polymerized, or neutralized by the broadly the distillation of such liquid mixtures into several fractions of different boiling points; the partial removal, polymerization, or neutralization of the impurities in one or more of these fractions; the subsequent-addition thereto of a proper proportion of another fraction or fractions; the completion of the removal, polymerization, or neutralization of the impurities, and the redistillation of the resulting mixture.

Variations may be made in the washing method and other variations may be made without departing from my invention.

I claim: 7

1. The method of treating distillates, consisting in partly chemically purifying a temperature fraction, mixing it with another temperature fraction, and chemically purifying the mixture. 1

2. The method of treating distillates, consisting in partly chemically purifying a lower boiling point fraction, adding thereto a higher boiling point fraction, and chemically purifying the mixture.

3. The method of treating distillates, consisting in partly chemically purifying a lower boiling point 'fraction, adding thereto a higher boiling point fraction, chemically purifying the, mixture, and distilling the mixture to separate the purified fractions. i c v 4. The method of treating light oil distillates, consisting in partly chemically purifyingthe lowers fraction including toluol, mixing therewith a higher distillate fraction, and chemically purifying the mixture.

In testimony whereof, I have hereunto'set my hand.

FREDERICK W. SPERR, JR: Witnesses:

JEssE B. HELLER, GEo. B. BLmnNe. 

